Conventionally, for the purpose of assisting the visibility when driving at night, a night vision apparatus for a vehicle is known in which light is irradiated using an illuminating device such as a headlamp that emits visible light and infrared light in a traveling direction such as the forward direction of the vehicle, an image of light reflected from a subject is captured using an imaging element of a camera, and the image is displayed on a monitor inside the vehicle.
For example, Japanese Unexamined Patent Publication JP-A 2004-142561 discloses a configuration in which with respect to a light source that emits light having a wavelength ranging from the ultraviolet light region to the infrared light region, two filters are used to absorb light in the visible light region (380 to 780 nm) and to pass light in the infrared light region (780 nm or more), so that an image that is not be tinged with red can be displayed using infrared transmission light, and the field of view at night or in bad weather can be enlarged without dazzling a driver of an oncoming vehicle.
Furthermore, Japanese Unexamined Patent Publication JP-A 2003-259363 discloses a method for making an obstacle such as a pedestrian hidden in halation more visible, by reducing halation in an image, by performing data processing to lower the brightness of a high intensity portion that causes halation so that halation from a high intensity light source does not occur.
Moreover, in these night vision apparatuses, a night vision apparatus for a vehicle is being developed in which infrared light is used for capturing information on a distant area that is not visible, visible light is used for capturing information on the vicinity of the vehicle, and both pieces of information are displayed on a display inside the vehicle.
However, in a case where light throughout the entire visible light region is absorbed as in JP-A 2004-142561, an image displayed is based on only infrared transmission light. Thus, when displaying an image around the vehicle based on signals of the visible light region, for example, when detecting an obstacle such as a pedestrian who is present near the vehicle or when recognizing a white line, the sensitivity of an image is lowered. Accordingly, there is the problem that an obstacle such as a pedestrian around the vehicle cannot be recognized, or a white line drawn near the vehicle cannot be confirmed. Furthermore, with a method for lowering the brightness of a high intensity portion that causes halation as in JP-A 2003-259363, the brightness is lowered over the entire visible light region, because the peak wavelength of a light source causing halation exists over the entire visible light region as shown in FIGS. 4A and 4B. Thus, it cannot be said that an obstacle around the vehicle and a white line can be sufficiently confirmed.